Epstein-Barr virus (EBV) is an orally-transmitted human herpesvirus that establishes persistent infections in almost all adults worldwide. The reservoir of virus is in a latent state in the memory B cell population but current models suggest that it is replenished by sporadic reactivation in terminally differentiating plasmablasts, amplification in epithelial cells and reinfection of the B cell pool. Long term carriage of EBV can be associated with both lymphoid and epithelial malignancies and individuals who are immunosuppressed, particularly those infected with the human immunodeficiency virus (HIV), are at increased risk of developing them. Part of this increased risk may reflect a loss of control of replication of virus. The role that EBV plays in tumorigenesis is complex, but seroepidemiologic studies suggest that the disturbance of the normal equilibrium and an increase in virus load precedes the appearance of malignancy. The long term goal of this research is to understand the dynamics of infection, particularly how virus traffics between B cells and epithelial cells to amplify within the host. Five EBV envelope proteins have been differentially implicated in virus entry into B cells and epithelial cells, gp350, gH, gL, gp42 and BMRF2. New work from this laboratory suggests that preneoplastic changes in epithelial cells may make them more susceptible to infection as they differentially express cell proteins important for interaction with gHgL and gp350 and activate those that can induce virus replication in adjacent B cells. Further, that a newly identified envelope protein, BDLF2, which interacts with and may be dependent on BMRF2 may be relevant to virus spread. The immediate goals of this application are to test these hypotheses. Aim one will use soluble forms of gHgL and ?v?6, cell-based fusion assays and Surface Plasmon Resonance to evaluate interactions between gHgL and ?v?6 in triggering virus-cell fusion. The possibility that additional integrins can mediate the same function will be explored, the downstream effects of gH binding to integrins on intracellular movement of virus will be examined and the expression of integrins on normal and dysplastic tissues in vivo will be determined. Aim two will explore the role that CR2 plays in increasing efficiency of epithelial cell infection. Expression of CR2 on dysplastic epithelial cells in vivo will be evaluated and the effects on infection of a gp350-stimulated interaction with formins will be determined by comparison of full length and truncated CR2. Aim three will investigate the role of the BMRF2/BDLF2 complex by making a BDLF2-null virus and a BMRF2-null virus. A virus lacking the BMRF2 RGD motif will also be made to explore unique effects of gH and BMRF2 binding to integrins. EBV is one of a several viruses associated with oral complications of HIV disease reflecting its continued replication and shedding in the oropharynx. Unraveling mechanisms by which virus is targeted to cells newly prone to infection is important to understanding pathogenesis and developing evasive strategies PUBLIC HEALTH RELEVANCE: Epstein-Barr virus (EBV) is associated with several different malignancies and individuals with the human immunodeficiency virus are at increased risk of developing them. Part of this increased risk may represent a failure of the immune system to control EBV replication in epithelial cells. This application seeks to understand the interactions between virus and cell proteins that enable virus to enter epithelial cells and initiate replication and in doing so seeks to identify risk factors and potential novel therapeutic targets.